Ignition Switch RUN terminal wire R/LG always hot

[IDIBRONCO]

Lawrence Koepke, to add more to my above post, the glow plug controller being behind the intake is only done by Ford on a N/A set up. The controller is relocated to the top of the passenger's side valve cover with a Factory Turbo set up. That should tell us something. My thought is that if you even have a question or a doubt, then go ahead and relocate the controller.

 

[Farmer Rock]

My 87 IH s1600 with the 7.3 style controller is mounted on the rear of the engine under the air filter just like the fords . I will be relocating the relay on both my trucks, and doing away with the controller since I have manual GPs. I am really looking forward to cleaning up all the wiring some more in the engine bay. The PO loved wire nuts and taps. The electrical tape is another story. I am debating between fender mount and valve cover mount. I would guess the controller is located there because it was closer to the GPs, and since the engines were originally designed as N/A, maintenance wasn't really an issue since you could just pop off the air filter and the controller is right there.



Rock

 

[Farmer Rock]

Also, doesn't the 6.9 style plumb into to the water jacket? My trucks have the 7.3 style, so I am not to familiar with the 6.9 controller, but that would be the main reason it's located there, and they just never changed it with the 7.3s



Rock

 

[71 Highboy]

Also, doesn't the 6.9 style plumb into to the water jacket? My trucks have the 7.3 style, so I am not to familiar with the 6.9 controller, but that would be the main reason it's located there, and they just never changed it with the 7.3s



Rock

You are correct. It screws into the water jacket there at the back. Mine just plugs the hole. No controller at all. The latching relay for the GP's is fender mounted, and Grounded by the button in the cab. I run mine at 6 volts as designed for twice as long in normal temps by feeding the relay from only one of my two heavy 6 v. batteries. In the pic you can see the ground post from the block. The post on this battery feeds the relay, as well as the neg post on the other battery to make 12 for everything else. The 2 red wires at the top are from the latching relay on the fender to the old stock plug on the harness.

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[Lawrence Koepke]

Ah, that clears up a mystery, as to why on the back of the manifold. My experience tells me that items are mounted on the manifold for either vacuum or coolant. I gather it's still there on the 7.3 because "that's the way we've always done it", and "that's where the mounting holes are".
Wow. Two 6 V batteries. Makes sense, as they often have more AH. I had two 6 volt batteries in my '66 MGB, one on either side of the drive shaft behind the seats. I always figured it was for weight balance ;-). Of course, being British, they were positive ground.
I've decided the plate on the passenger fender is an ideal mounting spot for the relay/controller, unless somebody knows better.

 

[Farmer Rock]

You are correct. It screws into the water jacket there at the back. Mine just plugs the hole. No controller at all. The latching relay for the GP's is fender mounted, and Grounded by the button in the cab. I run mine at 6 volts as designed for twice as long in normal temps by feeding the relay from only one of my two heavy 6 v. batteries. In the pic you can see the ground post from the block. The post on this battery feeds the relay, as well as the neg post on the other battery to make 12 for everything else. The 2 red wires at the top are from the latching relay on the fender to the old stock plug on the harness.

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Being that you are using manual GPs, wouldn't it have been easier to use the 7.3 plugs (ZD9) since they are 12v. Then you could have used 12v batteries. All you would have to do is change the connectors. Wiring is the same, but the ZD9s are more durable, and take more glow time. I am in the process of re locating my GP relays, and am just looking forward to not having to sit on my knee caps trying to get all the way back there as I do now
BTW, I saw your thread in the introduction section, and that is a really awesome truck you built. I have always wanted to swap an idi in a highboy, I think they are some of the best looking trucks ever made.


Rock

 

[71 Highboy]

Being that you are using manual GPs, wouldn't it have been easier to use the 7.3 plugs (ZD9) since they are 12v. Then you could have used 12v batteries. All you would have to do is change the connectors. Wiring is the same, but the ZD9s are more durable, and take more glow time. I am in the process of re locating my GP relays, and am just looking forward to not having to sit on my knee caps trying to get all the way back there as I do now
BTW, I saw your thread in the introduction section, and that is a really awesome truck you built. I have always wanted to swap an idi in a highboy, I think they are some of the best looking trucks ever made.


Rock

I was familiar with the early starting issues of idi's before the better starters. They did not spin fast enough. I was also familiar with the amperage available from this system. It has not failed for almost thirty years, so I left it alone. Just sharing knowledge gained thru experience for those doing what we do... Thanks for the kudo's on the truck.

 

[Lawrence Koepke]

I have performed a GlowPlugWire-ectomy in prep for moving the relay onto the passenger fender. The plan is the use 4 AWG wire to and from the relay, one cable only to the rear of the engine, tied to the glow plug wires. I've read the glow plugs can draw 200 amps, and Philip1 (above) ended up with a 300 A fuse, as the 250 was blowing in the cold. I looked up the specs on wire size and maximum current, and 4 Gauge wire has a maximum rating of 135 amps for chassis wiring. I understand these ratings are low, and are usually designed for a minimum current loss (i.e. 3%), but I'm wondering just how warm does the 4 gauge wire get for you folks who have done what I am planning to do?

 

[Lawrence Koepke]

I've been doing some number crunching on the glow plug wires. I had 2 factory 10 gauge wires with 14 Gauge fusible links in them. A 14 gauge fusible link is rated at 32 amps, so that suggests to me that a total of 64 amps is the maximum the factory wiring can handle, much less than what I have read the glow plugs can draw (200 amps or more). Where am I going wrong?

 

[ifrythings]

Fusable links don’t have an exact ratting and the big thing to remember when gauging wire and fuse size is time, a fuse could do 300% it’s rated current for 30 seconds before blowing, wire is rated on how much it will warm up over time vs current. 4ga wire mite have a half voltage drop across it and have to dissipate 100 watts of heat but it’s only for 15 seconds and you don’t even feel the wire warm up.

 

[franklin2]

He's right. All wires heat up, it's just how hot you want them to run. If you look at some of your sources, different types of insulation on the wire gives the wire a different amp rating, even though it's the same amount of copper in the wire. The higher rated temperature insulation on the wire allows you to run more current on the same wire, it will get a little warmer but the insulation will stand it.

Then you have the location of the wire. A wire bundled in with other wires will have a lower rating. A wire like yours out in the open by itself will handle more current, since it can dissipate heat more readily.

 

[Lawrence Koepke]

Well, I just opened up my harness, pulled out the unused glow plug wires to the old relay location, anf found to my delight that the ignition RUN wire and Warning light wire are just the right length to reach the new location on the passenger fender plate. So, maybe I should consider pulling that 4 Gauge wire back out of the bundle, for cooling purposes, but the factory wires were in there, so I don't really know. I'm thinking that 4 Gauge will hardly get warm, as it 4 gauge is rated higher than two 10 gauge wires. Finding out the ignition and warning wires reach the new location makes me wonder if Ford had considered moving the relay to that location during the design phase, but then stuck with the IH position just because ?